1. Field of the Invention
The present invention relates to novel thermally stable bisimido/p-allylaniline copolymers and to the preparation of such novel copolymers.
2. Description of the Prior Art
Polymers prepared by reacting an N,N'-bisimide of an unsaturated dicarboxylic acid, such as, for example, an N,N'-bismaleimide, with a diprimary diamine (French Patent No. 1,555,564) are known to this art. The amounts of N,N'-bisimide and diamine are selected such as to provide a ratio: number of moles of bisimide/number of moles of diamine equal to at least 1; furthermore, it is generally preferred that such ratio be lower than 50. Thermally stable resins are produced, which display marked resistance to severe thermal stresses.
In the aforementioned French Patent, it is also indicated that the preparation of these resins may be carried out in bulk, by heating reactants which have been thoroughly mixed beforehand, or in an inert polar diluent such as dimethylformamide, N-methyl-pyrrolidone or dimethylacetamide, it being possible for the latter process to be used, for example, when the application of the polymer makes it necessary to employ a solution thereof.
Finally, it too is indicated that, for many applications, it is advantageous to conduct the polymerization in two steps; in a first stage, a prepolymer is prepared by heating a thorough mixture of the two reactants to a temperature on the order of 100.degree. to 250.degree. C. The prepolymer obtained may be employed in the form of a solution, suspension or powder, or else may also be shaped merely by being cast hot. In a second stage, curing of the prepolymer may be effected by heating it to temperatures on the order of 350.degree., optionally under pressure.